How to change this Download Page Redirector URL Changle Method to using Button Id?

Question

   /* Set endpoint of url */

add_rewrite_endpoint('download', EP_PERMALINK);

function pixabin_download()
{
    add_rewrite_endpoint('download', EP_PERMALINK);
}
add_action('init', 'pixabin_download');

/* Set custom Safelink page template */

function pixabin_download_template()
{
    global $wp_query;
    // if the request is fail it will back to the main post
    if (!isset($wp_query->query_vars['download']) || !is_singular()) return;
    // include the custom safelink (download) template
    include get_template_directory() . '/template/download.php';
    exit;
}

add_action('template_redirect', 'pixabin_download_template');


/* Meta box in posts edit */

function download_details() {
    global $post;
    $download_name = get_post_meta($post->ID, 'download_name', true);
    $download_link = get_post_meta($post->ID, 'download_link', true);
?>

<b style="text-transform:capitalize">Download Link Title</b>
<p><input style="width:98%"  type="text" name="download_name" value="<?= $download_name ?>" /></p>

<b style="text-transform:capitalize">Download Link/URL</b>
<p><input style="width:98%"  type="text" name="download_link" value="<?= $download_link ?>" /></p>

<?php }

function add_post_metaboxes() {
    add_meta_box('download_details', 'Download Link Box', 'download_details', 'post', 'normal', 'high');
}

add_action( 'add_meta_boxes', 'add_post_metaboxes', 0 );

function wpwm_save_postdata( $post_id ) {
    // First we need to check if the current user is authorised to do this action.
    if ( 'page' == @$_REQUEST['post_type'] ) {
        if ( ! current_user_can( 'edit_page', $post_id ) )
            return;
    } else {
        if ( ! current_user_can( 'edit_post', $post_id ) )
            return;
    } 
    $wpwm_meta = array( 'download_name', 'download_link', );
    //if saving in a custom table, get post_ID
    $post_ID = @$_POST['post_ID'];
    foreach ($wpwm_meta as $meta_key) {
        if(isset($_POST[$meta_key])) update_post_meta($post_ID, $meta_key, $_POST[$meta_key]);
    }
}
add_action( 'save_post', 'wpwm_save_postdata' );